1. Field of the Invention
The present invention is related to a method for controlling operations of an input device, and more particularly to a method for controlling operations of an input device having a resistor matrix.
2. Description of the Prior Art
Please refer to FIG. 1, which is a schematic diagram of an input device 100 according to the prior art. The input device 100 has a power control circuit 110 and a switch matrix 120. The power control circuit 110 sequentially supplies voltages V1, V2, V3 and V4 to the switch matrix 120. The switch matrix 120 has a plurality of first traces 121, a plurality of second traces 122 and a plurality of switches P11 to P44. A first end of each of the switches P11 to P44 is coupled to one of the first traces 121, and a second end of each of the switches P11 to P44 is coupled to one of the second traces 122. Each of the second traces 122 is coupled to one of output terminals O1 to O4 of the input device 100.
When a user touches the input device 100, a switch located at the touch point is turned on. For example, when the user touches an area around the switch P11, the switch P11 is turned on. Since the switch P11 is turned on, when the power control circuit 110 supplies the voltage V1 to the switch matrix 120, a current flows from the power control circuit 110 through the switch P11 to the output terminal O1. Therefore, the location of the touch point of the input device 100 could be determined according to detected currents outputted from the output terminals O1 to O4 and the timing of sequentially applying the voltages V1, V2, V3 and V4 to the first traces 121.
However, when two or more touch points of the input device 100 are triggered at the same time, the input device 100 may miscalculate the locations of the touch points . For example, when the user touches an area around the switches P21, P12 and P22, the switches P21, P12 and P22 are turned on accordingly. Since the switches P21, P12 and P22 are turned on, when the power control circuit 110 supplies the voltage V1 to the switch matrix 120, a current I flows from the power control circuit 110 through the switch P21, P22 and P12 sequentially to the output terminal O1. Accordingly, the input device 100 miscalculates that the touch point is located on the position of the switch P11.